1990 Xj 4.0 engine assistance
09-25-2019, 10:43 PM
#16
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Only one way to find out. Put a new gasket on.
09-26-2019, 12:46 AM
#18
Senior Member
Cruiser: Is the Jeep engine computer of this vintage smart enough such that it does adaptive throttle position calibration for idle? I have an Audi that after it set awhile with a dead battery it would not idle, had no power and stumbled and backfired on attempted acceleration. Before that it idled beautifully. I had to buy software tools to recalibrate the ECU throttle body settings to get it to run. With the dead battery the ECU reset to factory new calibration and with normal gunk built up in the throttle body and plate it put required idle conditions way different from "new". I could not drive it enough to give it a chance to relearn. After cleaning a moderate amount of gunk where the throttle plate sets at idle the problem was corrected even after a dead battery/ECU reset.
I expect a '90 Renix was not that smart but with a new ECU in this Jeep and what looks like some crud in the throttle body it had me wondering if there was a learning mode it needed to go through.
While the throttle body is off I would carefully clean the throttle body and throttle plate for potential idle improvement.
I expect a '90 Renix was not that smart but with a new ECU in this Jeep and what looks like some crud in the throttle body it had me wondering if there was a learning mode it needed to go through.
While the throttle body is off I would carefully clean the throttle body and throttle plate for potential idle improvement.
Last edited by third coast; 09-26-2019 at 12:50 AM.
09-26-2019, 08:52 AM
#19
Senior Member
Being that the ECU is new, I would be less concerned with that. Clean and reinstall the throttle body appropriately. Then make sure that everything is bone dry, and try it again.
09-26-2019, 09:05 AM
#20
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
ECU does none of that stuff. In fact, they rarely fail. And when they do it's usually an injector driver that's been trying to actuate a stuck injector.
09-27-2019, 07:45 PM
#21
Newbie
Thread Starter
Update, replaces TPS, IAC, CPS, and gasket. Initially did not have spark, unplugged CPS and inspected pins. They were bent out to the sides, I'm guessing they werent plugging properly. Wiggled em to they we straight enough to plug, and she started right up.
Have a really high idle in park, about 2000 rpm. In drive it's about 1500 in drive with no foot on throttle. Drives good, other than the high idle. No backfires, stutters or knocks. Shifted fine.
I'm over at my buddies, I'm assuming the TPS needs to be adjusted so that's what were doin
Have a really high idle in park, about 2000 rpm. In drive it's about 1500 in drive with no foot on throttle. Drives good, other than the high idle. No backfires, stutters or knocks. Shifted fine.
I'm over at my buddies, I'm assuming the TPS needs to be adjusted so that's what were doin
Last edited by Scowmoo; 09-27-2019 at 10:51 PM.
09-27-2019, 11:05 PM
#22
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Update, replaces TPS, IAC, CPS, and gasket. Initially did not have spark, unplugged CPS and inspected pins. They were bent out to the sides, I'm guessing they werent plugging properly. Wiggled em to they we straight enough to plug, and she started right up.
Have a really high idle in park, about 2000 rpm. In drive it's about 1500 in drive with no foot on throttle. Drives good, other than the high idle. No backfires, stutters or knocks. Shifted fine.
I'm over at my buddies, I'm assuming the TPS needs to be adjusted so that's what were doin
Have a really high idle in park, about 2000 rpm. In drive it's about 1500 in drive with no foot on throttle. Drives good, other than the high idle. No backfires, stutters or knocks. Shifted fine.
I'm over at my buddies, I'm assuming the TPS needs to be adjusted so that's what were doin
Good plan.
09-28-2019, 01:08 AM
#23
Newbie
Thread Starter
So adjusted the TPS to the proper voltage, mine worked out to 0.8437; and it resulted in a slightly lower idle in drive, about 1000, but in park I'm still runnin 2k. As I took off from my buddies I had a quick backfire through the intake, 3 more, then nothing the rest of the way.
Tips on TPS and possibly causes of backfire? Vacuum gauge is rock steady healthy in park, but when shifter to drive the gauge reads "latent timing"
Tips on TPS and possibly causes of backfire? Vacuum gauge is rock steady healthy in park, but when shifter to drive the gauge reads "latent timing"
Last edited by Scowmoo; 09-28-2019 at 01:13 AM.
09-28-2019, 08:34 AM
#24
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Sometimes when you set the TPS, it takes a couple of starts to settle in.
What did you set it at % wise?
I'm wondering if your throttle body hasn't been dinked with by someone. Like the butterfly is partially open.....
What did you set it at % wise?
I'm wondering if your throttle body hasn't been dinked with by someone. Like the butterfly is partially open.....
09-28-2019, 02:14 PM
#26
Newbie
Thread Starter
So I used you guide to adjust the TPS, my reference voltage was 4.91 multiplied that by 17% to get a voltage of 0.8347 volts. Took awhile to get it tightened down without it fluctuating all over the place, but got it eventually.
It doesn't look like it's been messed with too much, it has just the slightest opening on the throttle in closed position
Not sure. My cable is broken where most peoples cable breaks after 30 years, that little black plastic cone with the spring though.
It doesn't look like it's been messed with too much, it has just the slightest opening on the throttle in closed position
Not sure. My cable is broken where most peoples cable breaks after 30 years, that little black plastic cone with the spring though.
Last edited by Scowmoo; 09-28-2019 at 02:16 PM.
09-28-2019, 09:10 PM
#27
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
So I used you guide to adjust the TPS, my reference voltage was 4.91 multiplied that by 17% to get a voltage of 0.8347 volts. Took awhile to get it tightened down without it fluctuating all over the place, but got it eventually.
It doesn't look like it's been messed with too much, it has just the slightest opening on the throttle in closed position
Not sure. My cable is broken where most peoples cable breaks after 30 years, that little black plastic cone with the spring though.
It doesn't look like it's been messed with too much, it has just the slightest opening on the throttle in closed position
Not sure. My cable is broken where most peoples cable breaks after 30 years, that little black plastic cone with the spring though.
RENIX THROTTLE BODY BUTTERFLY ADJUSTMENT
Okay. Let’s start from scratch.
First off, that’s not an idle adjustment screw. It’s a throttle butterfly stop screw. It’s purpose is to allow the butterfly to be as close to completely closed as it can be without binding or wearing into the throttle body. It was never intended to be adjusted in the field. But, Uncle Bob didn’t know that, did he?
Engine off. Back off the butterfly stop screw with a 3/32″ allen wrench until the butterfly is completely closed. Now. turn the screw in until the FAINTEST movement of the butterfly opening is detected. If you have a .003″ feeler gauge, or something that thick as measured with a caliper, use that to set the clearance. We’re talking sticky note paper here.
This can be done more easily with the throttle body removed. If you remove the throttle body, be sure to replace the gasket underneath it after thoroughly cleaning the old one off.
Readjust your Throttle Position Sensor.
09-30-2019, 12:45 AM
#28
Newbie
Thread Starter
Dbd
All manifold bolts are tight, throttle body is not messed with, fee per guage of .003 is all that fit. Pulled the valve cover..and well I have quite a bit of play in my rocker arms. I can push #4, #10, #11, and #12 quite a bit. Pretty sure I shouldnt be able to move em at all right?
I'm unsure of which valves which, but I'm pretty sure #4, #10, and #12 are all intake valves, correct?
I'm unsure of which valves which, but I'm pretty sure #4, #10, and #12 are all intake valves, correct?
09-30-2019, 07:09 AM
#29
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Year: 1990
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All manifold bolts are tight, throttle body is not messed with, fee per guage of .003 is all that fit. Pulled the valve cover..and well I have quite a bit of play in my rocker arms. I can push #4, #10, #11, and #12 quite a bit. Pretty sure I shouldnt be able to move em at all right?
I'm unsure of which valves which, but I'm pretty sure #4, #10, and #12 are all intake valves, correct?
I'm unsure of which valves which, but I'm pretty sure #4, #10, and #12 are all intake valves, correct?
